Could speedo signal be used to switch thermo-fan relay?

[Looonie]

So I'm thinking... and someone correct me if I'm wrong here...

With correct ducting forcing air from the front bumper area through the intercooler and radiator, fans are redundant over about 60-80kph?

So, is it possible to have the speedo output signal trigger a shut off relay for the thermo-fan?

The car in question is a GZ20 with digital speedo signal... I figure the speedo signal must output an increased voltage based upon speed... so what I envisage is having the thermo-fan running on a relay and triggered by a water temp sensor, with an override cut-out over 80kph...

This way from 0-80kph the fan would operate based upon water temperature from the sensor in the cold side piping, and when the vehicle hits 80kph the override would trigger a cut-out on this circuit so the fan won't run at all...

Am I making any sense here? Is this a good idea? Is it possible?

I have absolutely no clue with electricity, wiring and circuits... so if its a good idea and possible, please try to explain to me in the simplest terms how to make it work

[wa5]

Assuming that you are correct, and the fans become redundant after 60kph, why would you need to go to the trouble of adding extra things to go wrong to your cooling system. as they wouldnt be operating anyway.

[RA35GT]

Speedo signals generally change frequency in relation to speed.

If your engine reaches the thermo temp switch point when your doing over 80km/h wouldn't you still want to run the fans since the car is getting hot?

If the airflow through the rad is sufficient at high speed the temp won't go up and the thermo switch wont trip. i.e. it already regulates itself.

So while you could do it with the speed signal, a simple water temp switch is a lot simpler and works pretty well.

[auto351]

Hi,
what would you save by stopping the fan , maybe a bit of power?
if thing are working the fans wont be running at speeds over 80K as the air flow would keep things cool anyway.

If it was a voltage signal or even pulses then you could use a PCB to cut-out the fan, I have seen a unit that would do this but it was $130 ~$180 from memory.

Im thinking if it was a good Idea it would already be done by the ECU ?
If it was me I would let it run

[madmont]

I use a microswitch with a flap on it which I placed in the airflow to turn off my fans at 40KPH

[rob]

i use a more simpler method of chaining a monkey to my engine, once it gets too hot the monkey then flails his arms and legs in a particular sequence to select an array of 13 switches strategically placed around the engine bay. Once the sequence is input a signal is sent to charge an induction coil with terminals strapped to my testicles, once the coil reaches maximum charge the sound signature from the shriek i make is detected by a computer which authenticates that its indeed my voice and no one elses and thus actuates the thermo fans.

....hang on.... no wait i spent $30 on this

http://www.toymods.net/forums/showpo...9&postcount=29

whole thread
http://www.toymods.net/forums/showth...ermofan+switch

[Looonie]

Hi,
what would you save by stopping the fan , maybe a bit of power?
if thing are working the fans wont be running at speeds over 80K as the air flow would keep things cool anyway.

Cheers... I guess that thought never really occured to me, thats what I get for having ideas at 1am i suppose...

You're right, if the fan relay is run off a thermoswitch, then any other systems should be irrelevant as over 80kph if the airflow is keeping the temperature below the set point then the fan won't run anyway...

[LeeRoy]

The bigger problem would be if your fans are running at 60-80km/h then surely that is the least of your worries. Being triggered by a thermoswitch they will only be on when the engine is hot, so my concentration would be on cooling the engine down - bigger rad, ducting, even sealing the radiator against the body to better direct air through.

I'm going to assume you get into a bit of drifting, in which case due to the angles your car travels on a track, the radiator probably doesnt get too much direct air and may rely on the fans to pull air through.

[Toy77]

I had a problem, where this set up would have helped.

I had AU falcon thermo's on my last patrol, controlled by a temp switch. The problem was that the thermostat opening temp, was higher than i would have liked.

If i set my thermo temp switch with a decent gap from the thermostat - then the car would heat soak by the time the fans kicked in and the temp would go up heaps.

If i slowed down the massive flow from those fans would cool it down very quickly.

Unfortunately with the thermofan temp very close to the thermostat opening temp, on the highway the fans would run all the time.

This was a prob for me as i had twin batteries with auto charge diverter. with the second battery running a fridge. the charge set up would only charge the second battery when the primary one was full, and the voltage was over a certain point. Thus protecting your drive battery being flattened by all the accesories.

But the fans drew so much juice, the alternator wouldn't charge my 2nd battery on the highway. And this was a hassle on the way to fraser island. (on the freeway the voltage with the fans running was still over 12.5 volts, but needed 13 odd to switch the charge)

This is really a dribble post - but is a situation where this may have been handy...

Cheers
Stew

[CrUZida]

Does anyone else reckon that once you hit about 60-80kph any decent shrouded thermofan will slow down the air going through the radiator, and the system will get hotter ?

ie the fans would create a barrier of sorts ?

[thechuckster]

fan would feather if the air coming thru the radiator was faster than what it could draw thru the core.

fan would only be a barrier if it ran backwards or the motor did not allow it to overspeed.

Shroud may some effect but then we restart on the argument about air speed thru the radiator core and efficiency of core based on air-speed...

[CrUZida]

I suppose measuring the current would be the go.

[auto351]

i use a more simpler method of chaining a monkey to my engine,

....hang on.... no wait i spent $30 on this

The simple solutions are always the best, the only problem with your setup would be the ongoing cost of bananas or do you use peanuts?

[PlacentaJuan]

the kit you want is available fropm jaycar.

get a kit book from them (has HEAPS of useful info for people who want to learn about cars) and also HEAPS of cool kits you can build to do with cars.

there is one you can build that used an input signal (from a tach or speedo) to turn something on or off.